Method and apparatus for clarifying electrolyte



June 7, 1966 L. A. WILLIAMS METHOD AND APPARATUS FOR CLARIFYING ELECTROLYTE Filed June 12, 1962 INVENTOR.

United States Patent 3,255,097 METHOD AND APPARATUS FOR CLARIFYING ELECTROLYTE Lynn A. Williams, Winnetka, Ill., assignor to Anocut Engineering Company, Chicago, 111., a corporation of Illinois Filed June 12, 1962, Ser. No. 201,837

- 12 Claims. (Cl. 204l43) This invention relates to a method and apparatus for the clarifying of electrolyte used in electrolytic metal removal processes such as that disclosed, by way of example, in the copending application of Lynn A. Williams, Serial No. 772,960, filed November 10, 1958, for Electrolytic Shaping, now Patent No. 3,058,895, dated October 16, 1962, and in the copending application of Joseph L. Bender and Lynn A. Williams, Serial No. 37,766, filed June 21, 1960, for Electrolytic Cavity Sinking Apparatus and Method.

The object of this invention is to provide a simple and novel means of eliminating from the electrolyteused in such metalworking processes the products of decomposition of the metal work material which is removed during processing.

In electrolytic metalworking, it is possible to utilize two different kinds of electrolytes, one in which the work material which is removed by anodic action goes into a true solution in the electrolyte, and the other in which the work material is made to form insoluble salts, which usually go into electrolyte as finely divided particles.

This invention is concerned with electrolytes in which solid particles are formed. Typical of such electrolytes are those formed by solutions of common salt (NaCl) in water. Sometimes to the common salt solution there may be added other salts, such as sodium nitrate or sodium fluoride or phosphates or other additive materials for special purposes, particularly for the improvement of finish on the work material. It is also possible to add alkali for the working of such materials as tungsten or in some instances acids may be added. However, if the amount of acid is excessive, it will frequently happen that .the products of decomposition of the Work material go into true solution, and in that case the electrolyte falls into the class with which this invention is not concerned.

Typically, if a simple sodium chloride solution is used, having a concentration of the order of one percent on "ice settling must be great enough so that the velocities of motion within it are quite low, and this requirement for size increases both. the cost and the space occupied, sometimes to dimensions which are prohibitive for use in any ordinary factory.

It has been noted for quite a long period of time that the material can be removed also by one or another form of flotation process like the processes used in various mining operations.

This invention utilizes the principle of flotation for the purpose of obtaining separation, and an object of the invention is to achieve such separation with a minimum of apparatus extrinsic to that required in the metal removal process itself.

Briefly, the invention utilizes the fact that in this type of metalworking operation, hydrogen is formed along with some other gases, and these gases, particularly the hydrogen, are utilized in such a way that some of the gas which is formed is attached to the fiocs of work material, so that it floats quite readily to the surface of a storage tank, where it may be readily removed by skimming.

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawing of a single figure illustrating, schematically, the apparatus of the invention.

In the drawing there is'shown at the left the typical arrangement for the feeding of an electrode 10 by a movable ram 12 operated by power driving means so that the electrode may be advanced toward the work with a carefully controlled motion. The ram mechanism is mounted in a frame which also carries a work table, and it should be understood that the electrode is in one way or another electrically insulated from the work support, either by insulating the entirety of the ram mechanism from the remainder of the frame or by insulating the electrode mount intself from the face plate of the ram.

The ram is shown with a protective boot 14 so arranged as to prevent the ingress of electrolyte solution into the mechanism. The electrode proper is mounted in a hollow header 16 and is connected by a conductor 18 of adequate electrical capacity to the negative side of a power supply unit which is not shown, but which is capable of supplying a low voltage (5 to 15 volts, high density (100 to 8000 :amperes per square inch) direct up to a saturated solution, then when the work material is steel the decomposition product is found to be iron hydroxide. This is found in finely divided particles which, however, tend to coalesce or flocculate to form visible flocs. This material, if it is allowed to accumulate in the electrolyte supply system, gradually thickens the mixture and, if a excessive amount is allowed to accumulate in the system, it impairs its satisfactory operation. Thus, it is necessary to remove this material.

This may be done by filtration, but the nature of the material to be removed is such that the filter areas, and consequently, the size of filtering equipment, must be quite large. The material may also be removed by the use of a'centrifuge, but this equipment is also quite large and costly. The material may also be removed by use of a settling tank, and here the addition of coagulating agents is helpful. Still, the size of the tank required for current between the work piece W and the electrode 10. The work W is mounted on a work table 19 and is connected by a conductor 20 to the positive pole of the power supply unit (not shown).

The electrode 10, which is insulated on its interior and exterior surfaces, 'is here shown partly in section, and it should be understood that it has a central bore and a tip at the working end slightly larger than the diameter of the electrode after giving account to the external insulation which surrounds it.

Against the work itself, there is pressed by suitable clamps a feed bushing 22 having a narrowed sealing section 24 adapted to press against the work. The clamping means is shown symbolically by two arrows. It may take the form of mechanical clamps; toggle clamps, for example; or it may be of the hydraulically actuated type of the kind illustrated in the Bender and Williams application referred to above. The feed bushing carries a recess 26 into which a conduit 28 is passed, usually consisting of a drilled hole, terminating at its exterior por- 3 tion with a thread to receive the coupling of a feed hose 30. The feed hose 30 is adapted to deliver electrolyte under high pressure into the chamber 26.

The feed bushing 22, which is preferably made of an insulating material, is shown in section and is provided with a central bore through which the electrode passes. Into the central bore there are cut a number of labyrinth grooves 32, which increase the effectiveness of the seal between the guide bushing 22 and the electrode 10.

It should be understood. that. as the electrode 10 is advanced by the ram 12 toward and into the work W, electrolyte under a pressure of the order of 40 to 250 p.s.i. or more is introduced through the hose 3%) into the chamber 26 and passes from the chamber under the tip of the electrode into its central bore up into the manifold 16 and through a passage in the manifold out through a hose or conduit 34. As the electrode advances into the work, it cuts an opening slightly larger than the body of the electrode, partly because of a tendency to remove metal laterally, and partly because of the lateral extension of the tip at the working end of the electrode. There is, thus, a passage all the way around the electrode through which solution is forced from chamber 26 down along the sides of the electrode into the work and then up through the middle of electrode and out through the manifold 16 and conduit or hose 34.

The electrolyte is supplied by a pressure pump 36. The outlet of the pump communicates through conduit 38 to a T connection from which a bypass line 49 extends with a valve V1 inserted therein. The other branch of the T leads through conduit 42 through valve V2 through a filter, and thence to the conduit 30 which feeds the electrolyte into the chamber 26 of the feed bushing 22. Pressure gauges G1 and G2 are inserted respectively ahead of the bypass valve V1 and behind the feed valve V2. Another gauge GZa may be inserted beyond the filter, as shown, so that in this way any pressure drop across the filter may be detected. The filter here used is of relatively small size and is intended to protect against introduction of foreign partices, chips of metal, dirt, etc., and is not intended to remove the decomposed work material.

The electrolyte supply tank generally designated by the reference numeral 44 is divided by a partition 50 into a clear well 46 and a flotation well 48. A conduit 52 is arranged to extend into the flotation well to a distance about one-third the height of the tank from its bottom and provide a passage through the partition 50 into the clear well at a level several inches below the top of the tank. Thus, when the level of liquid in the flotation well rises above the height of the upper limit of conduit 52, there will be a flow of liquid from the flotation well 48 into the clear well 46 through conduit 52, provided, of course, that the level in the clear well is lower than that of the liquid in the flotation well. The right-hand wall 54 of the flotation well has a portion 55 which is slightly cut away at its upper edge, and a gutter 56 is welded to it, the gutter being closed at its ends. The purpose of the gutter is to provide a convenient receptacle into which the accumulated flotated work material can be swept by skimming. A valved conduit 58 is arranged to permit emptying the sludge-like material from the gutter 56 either into a drain 60 or, if desired, into a barrel or other receptacle.

Turning back now to trace the flow of electrolyte after it leaves the electrode 10 through conduit or tube 34, the used electrolyte passes through the conduit 34, which is flexible to accommodate movement of the electrode, and connects to a rigid conduit or pipe 62. A gauge G3 is connected into this line, and the line is of size large enough so that the reading at gauge G3 indicates the back pressure within the hollow central portion of the electrode 10. This back pressure is controlled by a valve V3 in line 62 and is found near the right side of the drawing just prior to the plate where conduit 62 enters into the flotation well 48 of the tank 44. Conduit 62 terminates in a manifold tube 64 set as a cross T against the end of the conduit 4 62. This manifold tube extends across the width of the flotation well 48 and is provided with numerous small holes along its sides.

In operation, the used electrolyte passes through the flexible hose 34 into the conduit 62, through the valve V3, and then exits into the flotation well 48 through the manifold tube 64. Ordinarily, the valve V3 is adjusted in such a way that there is a back pressure, as indicated at the gauge G3, of the order of approximately one-third of the inlet pressure as measured at gauge G2a. In a typical operating condition, the inlet pressure will be 200 psi. and the exit pressure will be of the order of 50 to 75 p. s.i.

In the electrolysis at the work face, where the metal is removed from the work material in order to sink a cavity in it, hydrogen is liberated at the working surface of the electrode, which is connected negatively as a cathode. Some of this hydrogen seems actually to be dissolved in the liquid under this operating pressure, and some of it appears to be in the form of small bubbles. When the mixture of used electrolyte containing hydrogen is discharged through the manifold 64, there is, of course, a bubbling of the gases, and apparently the gases attach themselves to the flocs of work material which are formed in such a way that they float to the surface, where they accumulate and may be cleared away by skimming with a board or stick to which a strip of screen is attached. This material is skimmed or swept away from time to time by hand into the gutter 56, from which it may be drained away in any suitable manner.

It is feasible to remove the floated material by blowing air across the surface of the electrolyte in the flotation well 48, and air nozzles are provided at an appropriate angle to blow a stream of air toward the portion 55 of the wall 54 which is cut away above the gutter 56. This air streamwill constantly remove the floated material. A cover 72 is provided to prevent inadvertent splattering of the material and electrolyte.

A tank 66 for makeup solution is shown, and is provided with a conduit 68 into which is placed a valve V4 so that from time to time makeup solution may be added to the clear well 46 to keep the entire level high enough in the floatation well so that the skimming of the scum of work material may be facilitated.

As the products of decomposition rise to the surface, the remainder of the liquid in the floatation well is substantially cleared of particles except only for some which may settle all the way to the bottom, where they remain. Thus, the conduit 52 does not extend all the way to the bottom but to a distance of the order of one-third the distance from the bottom to the surface, and at this point the liquid is substantially clear of solid material. Naturally, in operation liquid is withdrawn from the clear well 46 by the pressure pump 36, and that portion which passes through the electrode 10 is returned into the flotation well 48, so that the level in the flotation well tends to rise until a flow is commenced through the conduit 52 to replenish the supply in the clear well. The'portion of liquid which is passed through the bypass system through conduit 40 does not, of course, affect the total amount of liquid available at any time in the clear well, as it is simply recirculated. It is important to avoid recirculating any excess quantity of fluid in the flotation well 48, as excessive agitation will stir the scum which it is desired to have float to the surface back through the body of liquid in the flotation well.

While the system has been shown as providing for a circulation of electrolyte around the exterior of the electrode and out through its central opening, the same result may be obtained by carrying out the flow in the opposite direction, in which case the exit liquid comes out through conduit 30 leading from the feed bushing and is then carried back into the flotation well 48. At the same time, the pressurized electrolyte is introduced into conduit 34 and fed down through the central opening in the electrode 10.

his possible, of course, to arrange for float valves to control the introduction of makeup solution, and also to provide mechanical systems for skimming away thefloated scum of work material byproducts.

It important that the flotation well be large enough so as to permit introduction of the used electrolyte withoutexcessive turbulence. This, of course, depends upon the size of the electrode and the volume of electrolyte passed through it.

It ,will be seen that this apparatus and method permit separation of the work material by flotation, without the addition of any special equipment for aeration or the like, but it is not beyond the scope of the invention to supp ement the flotation well or by adding oils or other agen s, including flocculating agents, to improve the effecti ness of the system. In this regard, pine oil and hous hold detergents have proved effective.

If upplemental aeration is found desirable, a perforat d header 74 is provided adjacent the bottom of the flotat on well 43, and it is connected to an air line 76 havin a manually operated valve V5 therein. When the additi nal air is required, the valve V5 is opened, and

' entering the well 48 will supplement the gas enin the used electrolyte to float the eroded maas been shown and described, it will be apparent ous modifications and variations thereof may be m de without departing from the underlying principles of the invention. It is therefore desired, by the following claims, to include within the scope of the invention all such variations and modifications by which substantially the results of the invention may be obtained through the use of substantially the same or equivalent means.

What is claimed as new and desired to be secured by United States Letters Patent, is:

1. In the method of electrolytically removing material from an electrically conductive and electrochemically erodable workpiece wherein an electrolyte is pumped under pressure to and through a work gap between the workpiece and an electrode while an electrolyzing direct current is passed between the workpiece and the electrode in a sense to make the workpiece anodic, the improvement comprising recovering from the work gap electrolyte under pressure in which particles of eroded workpiece material and gas bubbles formed during the electrolysis are entrained, conducting the pressurized electrolyte and entrained material and bubbles to a tank, entering the pressurized electrolyte and entrained material and bubbles into the tank substantially below the surface of the electrolyte therein which is maintained at an appreciably lower pressure than that of the entering electrolyte and simultaneously releasing the pressure on the entering electrolyte, permitting the gas bubbles to float flocs of the eroded material to the surface of the electrolyte in the tank, periodically skimming the flocs of eroded material from the surface of the electrolyte in the tank, and transferring clarified electrolyte for reuse to a clear electrolyte tank without appreciably agitating the electrolyte and eroded material in the first tank.

2. In the method of electrolytically removing material from an electrically conductive and electrochemically erodable workpiece wherein an electrolyte is pumped under pressure to and through a work gap between the workpiece and an electrode while an electrolyzing direct current is passed between the workpiece and the electrode in a sense to make the workpiece anodic, the improvement comprising recovering from the work gap electrolyte under pressure in which insoluble salts of workpiece material and gas bubbles formed during the electrolysis are entrained, conducting the pressurized electrolyte and entrained salts and bubbles to a tank, entering the pressurized electrolyte and entrained salts and bubbles into the tank substantially below the surface of the electrolyte therein which is maintained at an appreciably lower pressure than that of the entering electrolyte and simultaneously releasing the pressure on the entering electrolyte, permitting the gas bubbles to float flocs of entrained salts to the surface of the electrolyte in the tank, periodically skimming the flocs of salts from the surface of the electrolyte in the tank, and withdrawing clarified electrolyte for reuse.

3. The method set forth in claim 2, wherein air under pressure is introduced into the lower region of the tank to assist in floating flocs of the salts to the surface of the electrolyte.

4. In the method of electrolytically removing material from an electrically conductive and electrochemically erodable workpiece wherein an electrolyte consisting largely of a chloride salt is pumped under pressure to and through a work gap between the workpiece and an electrode while an electrolyzing direct current is passed between the workpiece and the electrode in a sense to make the workpiece anodic, the improvement comprising recovering from the work gap used electrolyte under pressure in which insoluble salts of workpiece material and gas bubbles formed during the electrolysis are entrained, conducting the pressurized electrolyte and entrained salts and bubbles to a tank, entering the pressurized electrolyte and entrained salts and bubbles into the tank substantially below the surface of the electrolyte therein which is maintained at an appreciably lower pressure than that of the entering electrolyte and simultaneously releasing the pressure on the entering electrolyte to effect highly active bubbling, permitting the gas bubbles to float flocs of entrained salts to the surface of the electrolyte in the tank and other material to settle to the bottom of the tank, periodically skimming the flocs of salt from the surface of the electrolyte in the tank, and withdrawing clarified electrolyte for reuse to a clear electrolyte tank from a point well below the surface of the electrolyte in the first tank and above the level of the settled out material.

5. In apparatus for electrolytically removing material from an electrically conductive and electrochemically erodable workpiece having a shaping electrode adapted to be brought into close spacing relationship with a work piece to define a work gap, means for pumping electrolyte under pressure to and through the work gap, and means connected to the electrode and the workpiece to pass an electrolyzing current between the electrode and the workpiece in a sense to make the workpiece anodic, the combination comprising an electrolyte flotation tank and a clear electrolyte tank, conduit means having its inlet connected to receive used electrolyte under pressure from the work gap and having its outlet in said floatation tank well below the top thereof and substantially below the surface of the electrolyte therein, a restriction in said conduit means to limit flow therethrough and to place a back pressure on the electrolyte in the work gap, so that electrolyte under pressure in which are entrained material eroded from the workpiece and gas bubbles formed during the electrolytic action is conducted to and entered into said flotation tank where the gas bubbles float the material to the top of the electrolyte, from which the material may be skimmed, means whereby the electrolyte in said flotation tank is maintained at an appreciably lower pressure than the pressure of the elec trolyte received from said conduit means, a conduit connecting said flotation tank and said clear tank and having an inlet in said flotation tank substantially below the top thereof and an outlet adjacent the top of said clear tank so that a higher electrolyte level in said flotation tank will force clarified electrolyte from said flotation tank to said clear tank for reuse, and means for skimming floated material from the surface of the electrolyte in said flotation tank.

6. In apparatus for electrolytically removing material from an electrically conductive and electrochemically erodable workpiece having a shaping electrode adapted to be brought into close spacing relationship with a workpiece to define a work gap, means for pumping electrolyte under pressure to and through the work gap, and means connected to the electrode and the workpiece to pass an electrolyzing current between the electrode and the workpiece in a sense to make the workpiece anodic, the combination comprising a flotation tank and a clear tank, a manifold having a plurality of outlet openings therein in said flotation tank positioned closer to the bottom than the top thereof and substantially below the surface of the electrolyte therein, conduit means connecting said manifold to the work gap between the electrode and the workpiece, a valve in said conduit means to control flow therethrough and to place a back pressure on the electrolyte in the work gap, so that electrolyte under pressure in which are entrained material eroded from the workpiece and gas bubbles formed during the electrolytic action is conducted to and entered into said flotation tank where the gas bubbles float the material to the top of the electrolyte from which the material may be skimmed, and a conduit connecting said flotation tank means whereby the electrolyte in said flotation tank is maintained at an appreciably lower pressure than the pressure of the electrolyte received from said conduit means and said manifold, said clear tank and having an inlet in said flotation tank substantially below the top thereof and an outlet adjacent the top of said clear tank so that a higher electrolyte level in said flotation tank will force clarified electrolyte from said flotation tank to said clear tank for reuse, and means for skimming floated material from the surface of the electrolyte in said flotation tank.

7. In apparatus for electrolytically removing material from an electrically conductive and electrochemically erodable workpiece having a shaping electrode adapted to be brought into close spacing relationship with a workpiece to define a work gap, means for pumping electrolyte under pressure to and through the work gap, and

piece to define a work gap, means for pumping elm t4 lyte under pressure to and through the work gap, and means connected to the electrode and the workpi e to pass an electrolyzing current between the electr d and the workpiece in a sense to make the workpiece anodic, the combination comprising an electrolyte ank, a wall dividing said tank into a flotation well a a clear well, a manifold having a plurality of outlet openings therein in said flotation well positioned close to the)a ottom than the top thereof and substantially below the surface of the electrolyte therein, conduit means connecting said manifold to the work gap between the, electrode and the workpiece, a restriction in said conduit means to limit flow therethrough and to place a back pressure on the electrolyte in the work gap, so that electrolyte under pressure in which are entrained material eroded from the workpiece and gas bubbles formed during the electrolytic action is conducted to and entered into said flotation well where the gas bubbles float the material to the top of the electrolyte from which the material may be skimmed, means whereby the electrolyte in said flotation well is maintained at an' appreciably lower pressure than the pressure of the electrolyte received from said conduit means and said manifold, means for skimming floated material from the surface of the elec- I I trolyte in said flotation well, and a conduit through said means connected to the electrode and the workpiece to pass. an electrolyzing current between the electrode and the workpiece in a sense to make the workpiece anodic, the combination comprising an electrolyte tank, a wall dividing said tank into a flotation well and a clear well, a manifold having a plurality of outlet openings therein in said flotation well positioned closer to the bottom than the top thereof and substantially below the surface of the electrolyte therein, conduit means connecting said manifold to the Work gap between the electrode and the workpiece, a valve in said conduit means to control flow therethrough and to place a back pressure on the electrolyte in the work gap, so that electrolyte under pressure in which are entrained material eroded from the workpiece and gas bubbles formed during the electrolytic action is conducted to and entered into said flotation Well where the gas bubbles ,float the material to the top of the electrolyte from which the material may be skimmed, means whereby the electrolyte in said flotation well is maintained at an appreciably lower pressure than the pressure of the electrolyte received from said conduit means and said manifold, means for skimming floated material from the surface of the electrolyte in said flotation well, and a conduit through said wall between said flotation well and said clear well to transfer clarified electrolyte from said flotation well to said clear well for reuse.

8. In apparatus for electrolytically removing material from an electrically conductive and electrochemically erodable workpiece having a shaping electrode adapted to be brought into close spacing relationship with a workwall between said flotation well and said clear well and having an inlet in said flotation well substantially below the top thereof and remote from said manifold and an outlet adjacent the top of said clear well so that a higher electrolyte level in said flotation well will force clarified electrolyte from said flotation well to, said clear well for reuse.

9. In apparatus for electrolytically removing material from an electrically conductive and electrochemically erodable workpiece having a shaping electrode adapted to be brought into close spacing relationship with a workpiece to define a Work gap, means for pumping electrolyte under pressure to and through the work gap, and

means connected to the electrode and the workpiece to pass an electrolyzing current between the electrode and the workpiece in a sense to make the workpiece anodic, the combination comprising an electrolyte tank, a Wall dividing said tank into a flotation well and a clearwell, a manifold in said flotation well positioned closer to the bottom than the top thereof and substantially below the surface of the electrolyte therein, said manifold havmg a plurality of outlet openings therefrom, conduit means connecting said manifold to the Work gapbetween the electrode and the workpiece, a valve in said conduit means to control flow therethrough and to place a back pressure on the electrolyte in the work gap, so that electrolyte under pressure in which are entrained material eroded from the workpiece and gas bubbles formed during the electrolytic action is conducted to and entered into said flotation well where the gas bubbles float the material to the top of the electrolyte, means whereby the electrolyte in said flotation well is maintained at an appreciably lower pressure than the pres sure of the electrolyte received from said conduit means' well so that a high electrolyte level in said flotation well will force clarified electrolyte from said flotation well to said clear well for reuse.

10. The method set forth in claim 2, wherein the floated fiocs 'are removed by blowing a stream of air across the surface of the electrolyte.

11. Apparatus as set forth in claim 5, wherein said skimming means includes means for blowing a stream of air across the surface of the electrolyte in said flotation tank to remove the floated material.

12. Apparatus as set forth in claim 5, including means adjacent the bottom of the flotation tank to provide supplemental air for floating the eroded material to .the surface of the electrolyte.

References Cited by the Examiner UNITED STATES PATENTS 1,376,459 5/1921 Pedersen 2l044 2,765,919 10/1956 Juell 21044 2,895,814 7/1959 Clark 204143 2,939,825 6/1960 Faust et a1. 204-143 FOREIGN PATENTS 335,003 9/1930 Great Britain.

JOHN H. MACK, Primary Examiner.

v R. L. GOQCH, R. MIHALEK, Assistant Examiners.

Dedication 3,255,097.Ly1m A. Williams, \Vinnetka, I11. METHOD AND APPARATUS FOR CLARIFYIN G ELECTROLYTE. Patent dated June 7, 1966. Dedication filed Dec. 23, 1971, by the assignee, Anocut Engineem'ng Company. Hereby dedlcates to the Public the portion of the term of the patent subsequent; to Dec. 24, 1971.

[Ofiim'al Gazette April 18, 1.972.] 

1. IN THE METHOD OF ELECTROLYTICALLY REMOVING MATERIAL FROM AN ELECTRICALLY CONDUCTIVE AND ELECTROCHEMICALLY ERODABLE WORKPIECE WHEREIN AN ELECTROLYTE IS PUMPED UNDER PRESSURE TO AND THROUGH A WORK GAP BETWEEN THE WORKPIECE AND AN ELECTRODE WHILE AN ELECTROLYZING DIRECT CURRENT IS PASSED BETWEEN THE WORKPIECE AND THE ELECTRODE IN A SENSE TO MAKE THE WORKPIECE ANODIC, THE IMPROVEMENT COMPRISING RECOVERING FROM THE WORK GAP ELECTROLYTE UNDER PRESSURE IN WHICH PARTICLES OF ERODED WORKPIECE MATERIAL AND GAS BUBBLES FORMED DURING THE ELECTROLYSIS ARE ENTRAINED, CONDUCTING THE PRESSURIZED ELECTROLYTE AND ENTRAINED MATERIAL AND BUBBLES TO A TANK, ENTERING THE PRESSURIZED ELECTROLYTE AND ENTRAINED MATERIAL AND BUBBLES INTO THE TANK SUBSTANTIALLY BELOW THE SURFACE OF THE ELECTROLYTE THEREIN WHICH IS MAINTAINED AT AN APPRECIABLY LOWER PRESSURE THAN THAT OF THE ENTERING ELECTROLYTE AND SINULTANEOUSLY RELEASING THE PRESSURE ON THE ENTERING ELECTROLYTE, PERMITTING THE GAS BUBBLES TO FLOAT FLOCS OF ERODED MATERIAL TO THE SURFACE OF THE ELECTROLYTE IN THE TANK, PERIODICALLY SKIMMING THE FLOCS OF ERODED MATERIAL FROM THE SURFACE OF THE ELECTROLYTE IN THE TANK, AND TRANSFERRING CLARIFIED ELECTROLYTE FOR REUSE TO A CLEAR ELECTROLYTE TANK WITHOUT APPRECIABLY AGITATING THE ELECTROLYTE AND EORDED MATERIAL IN THE FIRST TANK. 